The settling zone refers to the space enclosed by a covered skirtboard at a transfer point, sometimes including an additional enclosed volume of the load zone after the product has been placed onto the belt. This enlarged portion of the skirboard that composes the settling zone allows for the air moving through the transfer point to slow down so that dust is allowed to settle, rather than escaping.
The size of the settling zone depends on six factors: width and speed of the belt, chute width, amount of airflow, depth of the material bed, and diameter of the largest lump of material that may pass through the settling zone.
An increase in any of these factors requires a corresponding increase in the size of settling zone. Calculations to determine the size of a settling zone are for air space only – the area above the cargo. Measurements of the cross-sectional area of the chute exit should exclude the area occupied by material.
In addition to increasing the size, another way to slow down the air in the settling zone is the installation of rubber curtains as baffles. It is also important that any holes in the transfer point be closed, whether the opening arises from rust or wear or from an opened door.